(a) Field of the Invention
The invention relates to color optical filters, in particular, to color transmissive-reflective filters and can be used in color displays and devices for optical communication and information processing.
(b) Description of the Related Art
A known color filter of absorptive type transmitting incident light of the chosen spectral range and absorbing light of other spectral ranges, and the liquid crystal display including the filter are disclosed in U.S. Pat. No. 7,486,355. In this absorptive color filter, in particular, applied in liquid crystal displays, photoresist is used, painted over with dyes or their pigments. A drawback of this optical filter is the light energy loss at light absorption.
The color optical filter which reflects incident light of the chosen spectral ranges and transmits light of other spectral ranges, designed on the basis of layers cholesteric liquid crystals is known and disclosed in U.S. Pat. No. 6,573,961. This optical filter contained in the liquid crystal display is also described in the same patent. Drawbacks of this optical filter and the liquid crystal display including it are its relatively large thickness (not less than 5 micrometers), which makes it hard to place the filter between the plates of liquid crystal display without changing operating voltage values as the gap between the plates is 5-10 micrometers, and complexity of its fabrication.
The color optical filter of interference type, which transmits incident light of the chosen spectral range and reflects light of other spectral ranges consisting of alternating layers, with high and low refractive indices is known and disclosed in U.S. Pat. No. 7,924,374. This optical filter contained in the liquid crystal display also described in the same patent. However, the described optical filter allows eliminating absorption of light energy in it and in the display only at small working angles, not exceeding 10 degrees according to our estimations. This is serious disadvantage of this optical filter so application this filter in liquid crystal displays does not make any sense.
Metal-dielectric-metal interference optical filter of Fabry-Perot type, which transmits incident light of the chosen spectral range and reflects light of other spectral ranges, in which a dielectric layer is placed between two reflecting metal layers is known and disclosed in U.S. Pat. No. 7,811,725. This optical filter is placed on a substrate that is also described in the same patent, and applied, in particular, in the liquid crystal displays. The drawbacks of this optical filter are low light transmission of the chosen spectral ranges, not exceeding 70%, and small working angles, not exceeding 15 degrees according to our estimations.